import datetime
class Student:
    Name = ''
    Credits = 20.0
    def __init__(self,name=''):
        self.Name = name

class Transaction:
    def __init__(self, sender, recipient, value):
        if sender.Credits>value:
           sender.Credits -= value
           recipient.Credits += value
           self.time = datetime.datetime.now()
           print('Transaction finished at %s' %(self.time))

StuA = Student('A')
StuB = Student('B')
tran = Transaction(StuA,StuB,10)

print('Student: %s has %f credits' % (StuA.Name,StuA.Credits))
print('Student: %s has %f credits' % (StuB.Name,StuB.Credits))